Paint circuits

ABSTRACT

Methods and devices for forming painted circuits using multiple layers of electrically conductive paint. In one aspect, a painted circuit includes a substrate (111) and one or more paint layer (106, 108, 110, 112, 114, 116, 120, 122) applied to the substrate, where the one or more paint layers each form an electrical component of the painted circuit. A given paint layer of the one or more paint layers includes a conductive paint formulation having a resistance that is defined by a concentration of conductive material that is included in the conductive paint formulation and a thickness of the given paint layer, and lower concentrations of the conductive material included in the conductive paint formulation provide a higher resistance than higher concentrations of conductive material.

This application is a national stage application under 35 U.S.C. § 371of PCT International Application No. PCT/US2018/049663, filed Sep. 6,2018, which claims the benefit of U.S. Provisional Application Ser. No.62/558,579, filed Sep. 14, 2017. The contents of the foregoingapplications are hereby incorporated by reference.

BACKGROUND

Traditional solar cells use substrates with highly regular crystallinestructure, for example, crystalline silicon. Newer technologies includethin-film, amorphous solar cells to create discrete layers of individualmaterial with highly regular and predictable chemical structure.Commercial solar cell fabrication, in general, requires highlyspecialized equipment, which restricts fabricated solar cells togeographic locations with access to the complex manufacturing equipmentand/or specialized shipping and installation capabilities.

SUMMARY

This specification relates to paint circuits that can be formed usingmultiple layers of electrically conductive paint, and can, for example,be used to form solar paint circuit to convert sunlight intoelectricity.

In general, one innovative aspect of the subject matter described inthis specification can be embodied in a painted circuit including asubstrate and one or more paint layers applied to the substrate, wherethe one or more paint layers each form an electrical component of thepainted circuit. A first paint layer of the one or more paint layersincludes a conductive paint formulation having a resistance that isdefined by a concentration of conductive material that is included inthe conductive paint formulation and a thickness of the given paintlayer, and lower concentrations of the conductive material included inthe conductive paint formulation provide a higher resistance than higherconcentration of conductive material. Other embodiments of this aspectinclude corresponding systems, apparatus, and computer programs,configured to perform the actions of the methods, encoded on computerstorage devices.

These and other embodiments can each optionally include one or more ofthe following features. In some implementations, the painted circuit hasone or more paint layers of conductive paint including a battery anodepaint layer applied to the substrate, an ion bridge paint layer appliedto less than all of the battery anode paint layer, a battery cathodepaint layer applied to the ion bridge layer, a solar cell anode paintlayer applied to less than all of the battery cathode paint layer, aphotosensitized layer applied to the solar cell anode paint layer, asolar cell cathode paint layer applied to the photosensitized paintlayer, a diode paint circuit that is formed between the battery anodepaint layer and the solar cell cathode paint layer, and a transparentprotective layer applied to the solar cell cathode paint layer. Thediode paint circuit is physically separated from each of thephotosensitized paint layer, the solar cell anode paint layer, thebattery cathode paint layer, and the ion bridge paint layer and includesan electron conducting paint layer and a hole conducting paint layer.

In some implementations, the painted circuit includes a transistor layerapplied to less than all of the battery cathode layer and in electricalcontact with the solar cell anode paint layer, a light-emitting circuitthat is formed between the transistor paint layer and the transparentprotective layer, and a conductor paint layer that is formed between thebattery anode paint layer and the light-emitting circuit, wherein theconductor paint layer is physically separated from each of the ionbridge paint layer, the battery cathode paint layer, and the transistorpaint layer. The light-emitting circuit is physically separated from thephotosensitized paint layer and includes an electron conducting paintlayer, a hole conducting paint layer, and a phosphorescent orelectroluminescent paint layer between the electron conducting paintlayer and the hole conducting paint layer.

In some implementations, the transistor paint layer includes acomposition having a dielectric material that has a breakdown voltagethat corresponds to a switching voltage of the transistor paint layer.

In some implementations, the phosphorescent paint layer includes anaqueous composition having one or more luminescent materials in anacrylic material.

In some implementations, the painted circuit has one or more paintlayers of conductive paint, including an anode paint layer applied tothe substrate, an ion bridge paint layer applied to less than all of theanode paint layer, a photosensitized/battery cathode paint layer appliedto the ion bridge paint layer, a solar cell cathode paint layer appliedto less than all of the photosensitized/battery cathode paint layer, anda transparent protective layer applied to the solar cell cathode paintlayer.

In some implementations, the anode paint layer includes an aqueouscomposition having an anionic fast ion conductor and a salt in a weightratio of water. The salt in the weight ratio of water can bewater:salt:anionic fast ion conductor of 60:10:1.

In some implementations, the anode paint layer includes an electronacceptor, where the salt in the weight ratio of water:salt:electronacceptor:anionic fast ion conductor is 60:10:10:1. For example, theanode paint layer can include an anionic polyacrylamide in a weightratio of water:titanium dioxide:potassium iodide:anionic polyacrylamideof 60:10:10:1.

In some implementations, the photosensitized/battery cathode paint layerincludes an aqueous composition having a cationic fast ion conductor ina weight ratio of water, where the cationic fast ion conductor in theweight ratio of water is 60:1.

In some implementations, the photosensitized/battery cathode paint layerincludes a cationic polyacrylamide in a weight ratio of water:cationicpolyacrylamide of 60:1. The photosensitized-battery cathode paint layercan be an aqueous composition including a cationic fast ion conductorand a dye in a weight ratio of water:cationic fast ion conductor:dye of6:1:1. For example, the photosensitized/battery cathode paint layerincludes a cationic polyacrylamide and copper phthalocyanine in a weightratio of water:cationic polyacrylamide:copper phthalocyanine of 6:1:1.

In some implementations, the ion bridge paint layer includes an aqueouscomposition having an ionic material and an ion-conducting polymer in aweight ratio of water.

In some implementations, the painted circuit has two or more contacts,each contact including a metallic foil affixed to a battery anode paintlayer or a battery cathode paint layer and in electrical contact withthe battery anode paint layer or the battery cathode paint layer,respectively.

In some implementations, the one or more paint layers of conductivepaint include a solar cell anode paint layer applied to the substrate, aphotosensitized paint layer applied to less than all of the solar cellanode paint layer, an output regulator circuit that is formed on top ofthe solar cell anode paint layer, a solar cell cathode paint layerapplied to the photosensitized paint layer and the transistor paintlayer, and a transparent protective paint layer applied to the solarcell cathode paint layer. The output regulator circuit includes aresistor paint layer and transistor paint layer, where the resistorpaint layer is applied to the solar cell anode paint layer and isapplied adjacent to the photosensitized layer, and the transistor paintlayer is applied to the resistor paint layer.

In some implementations, the resistor paint layer includes an aqueouscomposition having an acrylic material and carbon black suspended in theacrylic material, where a weight ratio of carbon black in the acrylicmaterial determines, in part, a resistance of the resistor paint layer.

In some implementations, the transistor paint layer includes acomposition having a dielectric material that has a breakdown voltagethat corresponds to a switching voltage of the transistor paint layer.

In some implementations, the solar cell cathode paint layer includes anaqueous composition having a cationic fast ion conductor in a weightratio of water, where the cationic fast ion conductor in the weightratio of water is 60:1.

In some implementations, the photosensitized paint layer includes anaqueous composition having an anionic fast ion conductor and a dye in aweight ratio of water:anionic fast ion conductor:dye of 6:1:1.

In general, another aspect of the subject matter described in thisspecification can be embodied in methods that include a process formanufacturing a painted circuit including, providing a substrate andapplying one or more paint layers on a surface of the substrate, the oneor more paint layers each forming an electrical component of the paintcircuit element. A first paint layer of the one or more paint layersincludes a conductive paint formulation having a resistance that isdefined by a concentration of conductive material that is included inthe conductive paint formulation and a thickness of the given paintlayer, and wherein lower concentrations of the conductive materialincluded in the conductive paint formulation provide a higher resistancethan higher concentrations of conductive material. Other embodiments ofthis aspect include corresponding systems, apparatus, and computerprograms, configured to perform the actions of the methods, encoded oncomputer storage devices.

These and other embodiments can each optionally include one or more ofthe following features. In some implementations, a process formanufacturing a painted circuit includes applying a battery anode paintto the substrate to yield a layer of the battery anode paint in directcontact with the substrate, applying an ion bridge paint to less thanall of the battery anode paint layer to yield a layer of ion bridgepaint in direct contact with the battery anode paint layer, applying abattery cathode paint to the ion bridge paint layer to yield a layer ofbattery cathode paint in direct contact with the ion bridge paint layer,applying a solar cell anode paint to less than all of the batterycathode paint layer to yield a layer of solar cell anode paint in directcontact with the battery cathode paint layer, applying a photosensitizedpaint to the solar cell anode paint layer to yield a layer ofphotosensitized paint in direct contact with the solar cell anode paintlayer, applying a solar cell cathode paint to the photosensitized paintlayer to yield a layer of solar cell cathode paint in direct contactwith the photosensitized paint layer, forming a diode paint circuitbetween the battery anode paint layer and the solar cell cathode layer,and applying a transparent protective paint to the solar cell cathodepaint layer to yield a layer of transparent protective paint in directcontact with the solar cell cathode paint layer. Forming a diode paintcircuit includes applying an electron conducting paint to less than allof the battery anode paint layer to yield a layer of electron conductingpaint in direct contact with the battery anode paint layer, and applyinga hole conducting paint to the electron conducting paint layer to yielda layer of hole conducting paint in direct contact with the electronconducting paint layer, where the diode paint circuit is formed and isphysically separated from each of the photosensitized paint layer, thesolar cell anode paint layer, the battery cathode paint layer, and theion bridge paint layer.

In some implementations, a process for manufacturing a painted circuitincludes applying a transistor paint to less than all of the batterycathode layer to yield a layer of transistor paint in direct contactwith the battery cathode layer and in electrical contact with the solarcell anode paint layer, forming a light-emitting circuit between thetransistor paint layer and the transparent protective paint layer, andapplying a conductor paint to less than all of the battery anode paintlayer to yield a layer of conductor paint in direct contact with thebattery anode paint layer and the light-emitting circuit and isphysically separated from each of the ion bridge paint layer, thebattery cathode paint layer, and the transistor paint layer. Forming alight-emitting circuit includes applying an electron conducting paint toless than all of the transistor paint layer to yield a layer of electronconducting paint in direct contact with the transistor paint layer,applying a phosphorescent paint to the electron conducting paint layerto yield a layer of phosphorescent paint in direct contact with theelectron conducting paint layer, applying a hole conducting paint to thephosphorescent paint layer to yield a layer of hole conducting paint indirect contact with the phosphorescent paint layer, where thelight-emitting circuit is formed and is physically separated from thephotosensitized paint layer.

In some implementations, a dielectric material is combined with a paintbinder to yield a mixture and yield a transistor paint.

In some implementations, a phosphorescent material is combined withwater to yield a mixture, and a polymer host material is dissolved inthe mixture to yield a phosphorescent paint.

In some implementations, a process for manufacturing a painted circuitincludes applying an anode paint to the substrate to yield a layer ofanode paint in direct contact with the substrate, applying an ion bridgepaint to less than all of the anode paint layer to yield a layer of ionbridge paint in direct contact with the anode paint layer, applying aphotosensitized/battery cathode paint to the ion bridge paint layer toyield a layer of photosensitized/battery cathode paint in direct contactwith the ion bridge paint layer, applying a solar cell cathode paint toless than all of the photosensitized/battery cathode paint layer toyield a layer of solar cell cathode paint in direct contact with thephotosensitized/battery cathode paint layer, and applying a transparentprotective layer paint to the solar cell cathode paint layer to yield alayer of transparent protective paint in direct contact with the solarcell cathode paint layer.

In some implementations, a cationic fast ion conductor is dissolved inwater to yield a hole transport paint.

In some implementations, a salt is dissolved in water to yield a saltsolution, an electron acceptor is combined with the salt solution toyield a mixture, and an anionic fast ion conductor is dissolved in themixture to yield an electron transport paint.

In some implementations, a dye is combined with water to yield amixture, and an anionic fast ion conductor is dissolved in the mixtureto yield a photosensitizing paint.

In some implementations, an ionic material is combined with water toyield a mixture, and an ionic-conducting material is dissolved in themixture to yield ion bridge paint.

In some implementations, a process for manufacturing a painted circuitincludes applying an electron transport paint to the substrate to yielda layer of the electron transport paint in direct contact with thesubstrate, applying an electroluminescent paint to the electrontransport paint layer to yield a layer of the electroluminescent paintin direct contact with the electron transport paint layer, and applyinga hole transport paint to the electroluminescent paint layer to yield alayer of the hole transport paint in direct contact with theelectroluminescent paint in direct contact with the electroluminescentpaint layer.

In some implementations, an electroluminescent material is combined withwater to yield a mixture, and a polymer host material is dissolved inthe mixture to yield an electroluminescent paint.

In some implementations, a process for manufacturing a painted circuitincludes applying an anode paint to the substrate to yield a layer ofanode paint in direct contact with the substrate, applying aphotosensitized paint to less than all of the solar cell anode paintlayer to yield a layer of photosensitized paint in direct contact withthe solar cell anode paint layer, forming an output regulator circuit ontop of the solar cell anode paint layer, applying a solar cell cathodepaint to the photosensitized paint layer and the transistor paint layerto yield a layer of solar cell cathode paint in direct contact with thephotosensitized paint layer and the transistor paint layer, and applyinga transparent protective paint to the solar cell cathode paint layer toyield a layer of transparent protective paint in direct contact with thesolar cell cathode paint layer. Forming an output regulator circuitincludes applying a resistor paint to less than all of the solar cellanode paint layer to yield a layer of resistor paint in direct contactwith the solar cell anode paint layer and adjacent and in electricalcontact to the photosensitized paint layer, and applying a transistorpaint to the resistor paint layer to yield a layer or transistor paintin direct contact with the resistor paint layer.

In some implementations, a conductive material is combined with water toyield a mixture, and an acrylic material is dissolved in the mixture toyield resistor/conductor paint.

In some implementations, a process for manufacturing a painted circuitincludes applying an electron transport paint to the substrate to yielda layer of the electron transport paint in direct contact with thesubstrate, applying a photosensitizing paint to the electron transportpaint layer to yield a layer of the photosensitizing paint in directcontact with the electron transport paint layer, and applying a holetransport paint to the photosensitizing paint layer to yield a layer ofthe hole transport paint in direct contact with the photosensitizingpaint in direct contact with the photosensitizing paint layer.

Particular embodiments of the subject matter described in thisspecification can be implemented to realize one or more of the followingadvantages. Unlike traditional commercial solar cell fabrication, solarpaint circuits can be fabricated with few tools (e.g., a hand mixer anda paint brush) by individuals in any location (e.g., even in remoteregions that do not have access to electricity or other resourcesrequired by conventional approaches). The solar paint circuits discussedherein are created using combinations of basic, inexpensive materials toform electronic circuits, which reduces fabrication complexity andreduces the cost to the manufacturer and end-user. In general, many ofthe materials used in the solar paint circuits are less hazardous andare less expensive to manufacture and ship than materials used intraditional solar cells. The paint circuits described here have areduced upfront capital expenditure requirement relative to traditionalcircuit fabrication and can be fabricated on-site as result, reducingimport/export tax or customs duty in countries where traditional circuitfabrication facilities cannot be established. Additionally, existinginfrastructure in commonly found paint factories can be converted easilyto produce solar paint circuits, whereas traditional solar cellfabrication requires highly specialized equipment. The relationshipbetween the electrically active material and its paint substrate enablethe electrical properties of the paint to be selected using relativelysimple mathematical analyses. Additionally, the ability to control theviscosity of the paint and/or the number of layers applied enables theelectrical characteristics to be easily changed by changing theviscosity and/or the number of layers of paint applied. This type offlexibility is typically unavailable with more conventional,high-precision circuit fabrication methods.

The details of one or more embodiments of the subject matter describedin this specification are set forth in the accompanying drawings and thedescription below. Other features, aspects, and advantages of thesubject matter will become apparent from the description, the drawings,and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are block diagrams of example solar paint circuits.

FIG. 2 is a block diagram of another example solar paint circuit.

FIG. 3 is a block diagram of another example solar paint circuit.

FIG. 4 is a flow chart of an example process for producingresistor/conductor paint.

FIG. 5 is a flow chart of another example process for producing ionbridge paint.

FIG. 6 is a flow chart of another example process for producingelectroluminescent and/or phosphorescent paint.

FIG. 7 is a flow chart of another example process for producing electrontransport paint.

FIG. 8 is a flow chart of another example process for producingphotosensitizing paint.

FIG. 9 is a flow chart of another example process for producing holetransport paint.

FIG. 10 is a flow chart of another example process for producingphotosensitized/battery cathode paint.

FIG. 11 is a flow chart of an example process for painting a paintcircuit.

FIG. 12 is a flow chart of another example process for painting a paintcircuit.

FIG. 13 is a flow chart of another example process for painting a paintcircuit.

FIG. 14 is a flow chart of another example process for painting a paintcircuit.

FIG. 15 is a flow chart of another example process for painting a paintcircuit.

FIG. 16 is a flow chart of another example process for painting a paintcircuit.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

Overview

Described below are devices, systems, and methods for producing solarpaint and solar paint circuits. A paint circuit (e.g., a solar paintcircuit) is created through a layer-by-layer application of electricallyconductive paint (e.g., solar paint) to a surface of a substrate. Thesubstrate can be, for example, a piece of wood, brick, plaster, stone,metal surface, or another surface to which paint can be applied. Theapplication of layers of solar paint to the substrate can be done byhand using a paintbrush or another form of simple spreading tool.

Though the term “solar paint circuit,” and “solar paint” are used in thecontext of describing particular embodiments of the subject matter, itis not meant to be limiting. Other paint circuits can be implementedwhich do not integrate solar energy (e.g., a battery, a light-emittingdiode, an antenna, or other circuit elements), as well as paint layersthat are not directly involved in forming solar-integrating circuits.

In some implementations, a painted circuit can be created by applying asingle paint layer to a substrate. For example, a simple resistivecircuit can be created by applying a single paint layer to thesubstrate. As discussed in more detail below, the paint layer applied tothe substrate can be a conductive paint formulation having a resistancethat is defined by a concentration of conductive material that isincluded in the conductive paint formulation and thickness of the paintlayer. In some implementations, when lower concentrations of theconductive material are included in the paint formulation, theresistance of the paint formulation will be higher than when higherconcentrations of the conductive material are included in the paintformulation.

In some implementations, a paint layer is applied through a template(e.g., a mask, stencil, and/or screen printing tool), such that paint isapplied to a substrate in a portion of the template but is preventedfrom being applied to the substrate in a second, different portion ofthe template.

In some implementations, multiple paint layers are applied to thesubstrate to create a painted circuit. For example, after a first layerof paint is applied to the portion of the substrate, other layers can beapplied to other portions of the substrate (e.g., adjacent to the firstlayer) and/or applied to already painted portions of the substrate(e.g., applied over the first layer of paint). Each layer of paint formsan electrical component of the painted circuit (e.g., an electrontransport layer, a hole transport layer, etc.).

A paint layer can include a conductive paint formulation where aresistance of the paint layer is defined by a concentration ofconductive material (e.g., carbon black) that is incorporated into theconductive paint formulation, and a thickness of the given paint layer.Paint layers with lower concentrations of conductive material in theconductive paint formulation will have higher resistances than paintlayers with higher concentrations of the conductive material. Adjustinga viscosity of the paint layer can change a thickness of the paint layerapplied to the substrate, which in turn will affect the resistance ofthe paint layer. For example, a paint formulation with a higherviscosity will result in a thicker paint layer than a paint formulationwith a lower viscosity, and thicker layers of paint will generally havehigher resistance in a direction perpendicular to the plane of the layerthan thinner layers of similar formulation.

As described in more detail below, various types of circuits and devicescan be fabricated using solar paint. Several examples circuits aredescribed below, but other circuits can be created using the techniquesdescribed below. Examples of solar paint circuits described belowinclude, a solar battery, where a solar cell charges a battery. Anotherexample of a solar paint circuit is a solar-powered streetlight,including a solar cell, a battery, and a light-emitting circuit. Anotherexample of a solar paint circuit is a solar cell including an outputregulator to regulate the solar cell to a maximum power point of thesolar cell, which can be used as part of a cell phone charging circuit.As described in more detail below, various circuit elements, such asresistors, capacitors, diodes, and transistors, can be fabricated usingthe solar paint described herein.

Though the example circuits described below are depicted in blockdiagram form as single layers of each respective paint layer, multipleapplications (e.g., multiple layers) of particular paint layers can beused to achieve desirable electrical and/or functional properties.Additionally, though the examples depicted below describe singlesub-circuits (e.g., a single solar cell, a single solar battery)integrated and/or painted on one paint circuit, multiple sub-circuitsmay be incorporated and/or painted to form a larger paint circuit (e.g.,multiple solar cells) to achieve desired device performance).

Example Solar Paint Circuits

FIG. 1A is a block diagram of an example solar paint circuit 100. Thesolar paint circuit 100 includes a solar battery 102, a solar cell 104,a transparent protective layer 124, and a diode paint circuit 118. Thesolar battery 102 is formed by a battery anode paint layer 106, an ionbridge paint layer 108, and a battery cathode paint layer 110. Thebattery anode paint layer 106 can be created using a painted layer thatis applied to a substrate 111 (e.g., a surface composed of wood, metal,plaster, stone, brick, or another paintable material). The battery anodepaint layer 106 forms an anode for the solar battery 102. The batteryanode paint layer 106 can be formed by an aqueous paint compositionincluding an anionic fast conductor and an electron acceptor.Formulations for the battery anode paint layer 106 are discussed infurther detail below.

In some implementations, rather than using a paint layer to form thebattery anode paint layer 106, an electrically conductive substrate 111(e.g., a metal surface) can be used as the battery anode. In someimplementations, rather than using a paint layer to form the batteryanode paint layer 106, an electrically conductive mesh and/or foil(e.g., a wire mesh) is affixed to the substrate 111 and can be used asthe battery anode.

The ion bridge paint layer 108 is applied to a portion of the batteryanode paint layer 106. The ion bridge paint layer 108 forms an ionbridge for the solar battery 102 as a pathway for ions to move betweenthe battery anode paint layer 106 to the battery cathode paint layer110. The ion bridge paint layer 108 can be formed by an aqueous paintcomposition including an ion-conductive polymer and an ionic material.Formulations for the ion bridge paint layer 108 are discussed in furtherdetail below. In some implementations, the ion bridge paint layer 108 isapplied in a manner such that less than all of the battery anode paintlayer 106 is covered by the ion bridge paint layer 108. For example, asshown in FIG. 1A, the ion bridge paint layer 108 does not cover theentirety of the battery anode paint layer 106.

The battery cathode paint layer 110 is applied to the ion bridge paintlayer 108. The battery cathode paint layer 110 forms a cathode for thesolar battery 102. The battery cathode paint layer 110 can be formed byan aqueous paint composition including a cationic fast ion conductor.Formulations for the battery cathode paint layer 110 are discussed infurther detail below. As shown, the top surface of the battery cathodepaint layer 110 is in physical and electrical contact with the solarcell 104, which is described in more detail below.

The solar cell 104 includes a solar cell anode paint layer 112, aphotosensitized paint layer 114, and a solar cell cathode layer 116.Solar cell 104 is an electrical device that converts the energy of light(e.g., sunlight) into electricity. Photons (e.g., sunlight) are absorbedin the photosensitized paint layer 114, and charge generation ofelectrons and holes occurs. The generated charges are then separated andthe electrons move towards the cathode and holes move towards the anode,respectively, to generate electricity.

The solar cell anode paint layer 112 is applied to at least a portion ofthe battery cathode paint layer 110. The solar cell anode paint layer112 forms an anode for the solar cell 104. In some implementations, thesolar cell anode paint layer 112 is applied in a manner such that lessthan the entirely of the battery cathode paint layer 110 is covered bythe solar cell anode paint layer 112. The photosensitized paint layer114 is applied to the solar cell anode paint layer 112.

The photosensitized paint layer 114 forms a layer where photons can beabsorbed and charge generation takes place in the solar cell 104. Thephotosensitized paint layer 114 can be formed from a paint compositionincluding a dye and an anionic fast ion conductor. Formulations for thephotosensitized paint layer 114 are discussed in further detail below.

The solar cell cathode paint layer 116 is applied to the photosensitizedpaint layer 114. The solar cell cathode paint layer 116 forms a cathodefor solar cell 104. The solar cell cathode paint layer 116 can betransparent or semi-transparent to allow light to reach thephotosensitized paint layer 114 below. In some implementations, ratherthan a solar cell cathode paint layer 116, an electrically conductivemesh (e.g., a wire mesh) is used as a cathode layer for solar cell 104.

A diode paint circuit 118 is formed between the battery anode paintlayer 106 and the solar cell cathode paint layer 116. The diode paintcircuit 118 forms a diode in which the flow of current is only allowedin a single direction under normal operation, for example, a forwarddirection from the solar cell 104 to the solar battery 102. The diodepaint circuit 118, under normal operations, prevents electricity fromflowing “backwards” from the solar battery 102 to the solar cell 104.The diode paint circuit 118 includes a p-type diode paint layer 120,which is applied to a portion of the battery anode paint layer 106, andan n-type diode paint layer 122, which is applied to the p-type diodepaint layer 120. The p-type diode paint layer 120 and the n-type diodepaint layer 122 form a p-n junction for the diode paint circuit 118. Atop surface of the n-type diode paint layer 122 is in physical andelectrical contact with the solar cell cathode paint layer 116, e.g.,the solar cell cathode paint layer is applied to the n-type diode paintlayer 122. The diode paint circuit 118 is physically separated from theion bridge paint layer 108, the battery cathode paint layer 110, thesolar cell anode paint layer 112, and the photosensitized paint layer114. The physical separation between the diode paint circuit 118 and theion bridge paint layer 108, the battery cathode paint layer 110, thesolar cell anode paint layer 112, and the photosensitized paint layer114 can be an air gap and/or filled with an electrically insulatingmaterial (e.g., a resin). Formulations for the p-type diode paint layer120 and the n-type diode paint layer 122 are discussed in further detailbelow.

In one example, a standalone diode paint circuit 118 is formed byapplying three layers of a p-type diode paint on top of an electricallyconductive substrate (e.g., aluminum foil) to form a p-type diode paintlayer 120 followed by applying two layers of an n-type diode paint ontop of the p-type diode paint layer 120 to form a n-type diode paintlayer 122. A top contact including a protective coating layer (e.g., alayer of indium tin oxide coated on a sheet of clear plastic film) isbrought into electrical and physical contact with the n-type diode paintlayer 122.

In some implementations, respective thicknesses of the p-type diodepaint layer 120 and the n-type diode paint layer 122 exceed respectivethreshold thicknesses such that the two layers form a p-n junction. Forexample, if the thickness of the p-type diode paint layer 120 and/or thethickness of the n-type diode paint layer 122 is below respectivethreshold, then a p-n junction is not formed (e.g. the diode 118 doesnot function as a p-n junction). In some implementations, a thresholdthickness is determined in part by the materials forming the n-typediode paint layer 122 and/or the p-type diode paint layer 120, as wellas an operating voltage for the p-n junction formed. In general, thethreshold thickness depends, in part, on a quantum tunneling limit ofthe layer, where above the threshold thickness quantum tunneling becomeshighly improbable. For example, a threshold thickness is on the order ofa few nanometers of paint layer in a direction normal to the substrate111.

In some implementations, respective thicknesses of the paint layers incontact with the diode 118 (e.g., battery anode paint layer 106 andsolar cell cathode paint layer 116) are below respective thresholdthicknesses such that a p-n junctions are not formed between the paintlayers in contact with the diode 118. For example, a p-n junction is notformed between the p-type diode paint layer 122 and the battery anodepaint layer 106 and a p-n junction is not formed between the n-typediode paint layer 122 and the solar cell cathode paint layer 116 inpart, because the battery anode paint layer 106 and the solar cellcathode paint layer 116 are below respective threshold thicknesses forforming a p-n junction.

A transparent protective paint layer 124 is applied to the solar cellcathode paint layer 116. The transparent protective paint layer 124 canbe a transparent protecting coating and can also be electricallyinsulating (e.g., laminate, polyurethane finish, shellac). In someimplementations, the transparent protective paint layer 124 encapsulatesa portion or all of the exposed surfaces of the solar circuit 100. Thetransparent protective paint layer 124 forms a protective layer overpart or all of the solar circuit 100 to protect the solar circuit 100paint layers from environmental effects (e.g., UV radiation, weather,water/humidity). In some implementations, the transparent protectivepaint layer 124 is semi-transparent, and/or only transparent to certainwavelengths ranges (e.g., transparent to visible wavelengths). In someimplementations, the transparent protective layer 216 is omitted,depending in part on application and/or environmental factors (e.g.,level of exposure to weather). When the transparent protective layer 216is omitted, the solar cell cathode paint layer 116 can function as aconductive protective layer (e.g., indium tin oxide).

The solar cell 104 operates to absorb photons from the ambientenvironment (e.g., solar rays) in the photosensitized paint layer 114,such that electron-hole pairs are formed within the photosensitizedpaint layer 114, and charge separation occurs between the solar cellanode paint layer 112 and the solar cell cathode paint layer 116. Theseparated charges are then used to charge (e.g., trickle charge) thesolar battery 102 by producing a charge imbalance across the ion bridge108, and using the diode paint circuit 118 as a blocking diode where thediode paint circuit 118 allows the solar cell 104 to charge the solarbattery 102 without allowing the solar battery 102 to discharge when adischarge voltage of the solar battery 102 is higher than a voltageacross the solar cell 104 (e.g., in the dark).

The solar circuit 100 can be combined with other circuit elements toproduce a solar-powered light (e.g., a solar-powered streetlight). FIG.1B is block diagram of an example solar paint circuit 150. The solarcircuit 150 includes a solar battery 102, a solar cell 104, and alight-emitting circuit 152. The solar cell 104 can be used to generateelectricity from sunlight to charge (e.g., trickle charge) the solarbattery 102, which can then be used to power a light-emitting circuit152. The powered light-emitting circuit 152 can emit light in aparticular range of wavelengths (e.g., visible light).

The light-emitting circuit 152 is electrically connected to the batterycathode paint layer 110 by a transistor paint layer 154, which functionsas a transistor. In some implementations, the transistor paint layer 154is applied to less than the entire battery cathode paint layer 110. Forexample, as shown in FIG. 1B, the transistor paint layer 154 is appliedto the portion of the battery cathode paint layer 110 that is notcovered by the solar cell anode paint layer 112. As shown, thetransistor paint layer 154 is in physical contact with the solar cellanode paint layer 112. That is, the transistor paint layer 154 and thesolar cell anode paint layer 112 are both applied to the battery cathodepaint layer 110 in adjacent layers (e.g., painted side-by-side).

The light-emitting circuit 152 is formed between the transistor paintlayer 154 and the transparent protective layer 124. The light-emittingcircuit 152 is physically separated from the photosensitized paint layer114 (e.g., an air gap or insulating materials is between thephotosensitized paint layer and the light-emitting circuit 152). Thelight-emitting circuit 152 can include an electron conducting paintlayer (e.g., an anode), a hole conducting paint layer (e.g., a cathode),and a light-emitting paint layer and/or electroluminescent paint layer(e.g., a light-emitting polymer) between the electron conducting paintlayer and the hole conducting paint layer.

The electron conducting paint layer, hole conducting paint layer andlight-emitting paint layer form a light-emitting diode, where electronsare provided into the light-emitting circuit 152 through the electronconducting paint layer and holes are provided into the light-emittingcircuit 152 through the hole conducting paint layer. Electrons and holesfrom the electron conducting paint layer and hole conducting paintlayers, respectively, recombine in the light-emitting layer and generatephotons of a particular wavelength. In some implementations, thelight-emitting paint layer is a phosphorescent paint layer. Thelight-emitting paint layer can be a fluorescent paint layer.

The light-emitting paint layer of the light-emitting circuit 152 canemit light vertically through a transparent hole conducting paint layerand the transparent protective layer 124, and/or laterally through oneor more edges of the light-emitting paint layer of the light-emittingcircuit 152.

A conductor paint layer 156 (or multiple conductor layers applied on topof each other) is formed between the battery anode paint layer 106 andthe light-emitting circuit 152. The conductor paint layer 156 forms aconductive path for a flow of current between the battery anode paintlayer 106 and the light-emitting circuit 152. The conductor paint layer156 can be formed from a paint composition including an acrylic materialand a conductive material (e.g., carbon black). Formulations forconductive paint is discussed in further detail below. The conductorpaint layer 156 is physically separated from the ion bridge paint layer108, the battery cathode paint layer 110, and the transistor paint layer154.

The conductor paint layer 156 acts as an electrical bridge between thebattery anode paint layer 106 and the light-emitting circuit 152, suchthat the solar battery 102 provides electrical charge to thelight-emitting circuit 152 to operate the light-emitting circuit 152(e.g., emit light). The transistor paint layer 154 electrically connectsthe light-emitting circuit 152 to the battery cathode paint layer 110 tocomplete the electrical circuit 158. The transistor paint layer 154 canoperate as a “switch” where the layer of transistor paint can beswitched “off” when a sum of voltages of a high-voltage side (e.g., avoltage at the battery anode 106) exceeds a certain application specificvalue, or can be switched “on” by applying an additional “base” voltageon a low-voltage side (e.g., a voltage at the battery cathode 110).

FIG. 2 is a block diagram of another example solar paint circuit 200.The output-regulated solar cell 200 includes a solar cell 202, similarto solar cell 104 described with reference to FIG. 1A, and an outputregulator circuit 204. Solar cell 202 includes a solar cell anode paintlayer 206 applied to a bottom contact 205 (e.g., a wire mesh or foil) ona surface of a substrate 207 (e.g., wood, fabric, plaster, etc.). Insome implementations, the solar cell anode paint layer 206 is applieddirectly to the substrate 207. In some implementations, rather than asolar cell anode paint layer 206, the substrate 207 is an electricallyconductive substrate (e.g., a metal foil or shingle), and aphotosensitized layer 208 is a first layer applied to the substrate 207.

A photosensitized paint layer 208 is applied to a portion of the solarcell anode paint layer 206. The photosensitized paint layer 208 can beapplied to less than the entirety of the solar cell anode paint layer206, such that a part of a top surface of the solar cell anode paintlayer 206 is exposed. The photosensitized paint layer 208 forms a layerwhere photons can be absorbed and charge generation takes place in thesolar cell 202.

A solar cell cathode paint layer 210 is applied to the photosensitizedpaint layer 208. The solar cell cathode paint layer 210 forms a cathodefor the solar cell 202. The solar cell cathode paint layer 210 can betransparent or semi-transparent to allow light to reach thephotosensitized paint layer 208 below. In some implementations, ratherthan a solar cell cathode paint layer 210, an electrically conductivemesh (e.g., a wire mesh) is used as a cathode layer for solar cell 202.

The output regulator circuit 204 is formed between an exposed surface ofthe solar cell anode paint layer 206 and the solar cell cathode paintlayer 210. The output regulator circuit 204 is formed to regulate theoutput of the solar cell 202 to its maximum power point (MPP). Theoutput regulator circuit 204 includes a resistor paint layer 212 andtransistor paint layer 214. The resistor paint layer 212 is applied tothe solar cell anode paint layer 206, such that the resistor layer 212is in physical and/or electrical contact with the photosensitized layer(e.g., the resistor paint layer 212 and photosensitized paint layer 208are applied adjacent to each other). The resistor paint layer 212 formsa resistor in the output regulator circuit 204.

The transistor paint layer 214 is applied to the resistor paint layer.The transistor paint layer 214 is in physical and electrical contactwith the solar cell cathode paint layer 210. The transistor paint layer214 forms a transistor in the output regulator circuit 204. In someimplementations, a portion of the solar cell cathode paint layer 210 isadjacent to the transistor paint layer 214. The solar cell cathode paintlayer 210 can be applied to a top surface of the transistor paint layer214.

In some implementations, a top contact 215 is formed on a top surface ofthe solar cell cathode paint layer 210. A top contact can include ametallic mesh (e.g., copper, tin, steel), or indium tin oxide.

A transparent protective layer 216 is applied to the top contact 215 orthe solar cell cathode paint layer 210. In some implementations, thetransparent protective layer 216 encapsulates a portion or all of theexposed surfaces of the output-regulated solar cell 200. In someimplementations, the top contact (e.g., indium tin oxide layer) is thetransparent protective layer. The transparent protective paint layer 216forms an electrically insulating and protective layer over part or allof the output-regulated solar cell 200 to protect the paint layers fromenvironmental effects (e.g., UV radiation, weather, water/humidity). Insome implementations, the transparent protective paint layer 216 issemi-transparent, and/or only transparent to certain wavelengths ranges(e.g., transparent to visible wavelengths). In some implementations, thetransparent protective layer 216 is omitted, depending in part onapplication and/or environmental factors (e.g., level of exposure toweather).

The output-regulated solar cell 200 is designed to regulate the outputof the solar cell 202 to its maximum power point (MPP). This can beaccomplished by selecting a formulation of the transistor paint layer214 such that a breakdown voltage of the transistor paint layer is equalto the solar cell 202 MPP. Additionally, the formulation of the resistorpaint layer 212 is selected such that the output voltage of the solarcell 202 remains equal to the breakdown voltage of the transistor paintlayer 214 during the operation of the output-regulated solar cell 200.Particular formulations for the respective layers are described in moredetail below.

In some implementations, multiple solar cells 202 are connected togetherin series with a single output regulator circuit 204 to control theoutput between the multiple solar cells 202. Connecting multiple solarcells 202 together in series can increase the amount of electricitygenerated and available to power another circuit (e.g., a light-emittingcircuit, a cell phone device, etc.) or charge a solar battery.

FIG. 3 is a block diagram of another example solar paint circuit. Thecondensed solar circuit 300 shown in FIG. 3 includes a solar battery 302and a solar cell 304, similarly to the solar circuit 100 described withreference to FIG. 1A, where the solar cell 304 can absorb photons (e.g.,sunlight) to generate electricity to charge solar battery 302. Thecondensed solar battery 300 includes multi-functional paint layers,where each of the paint layers can perform a function (e.g., is ancomponent of a circuit element) for both the solar battery 302 and thesolar cell 304. For example, an anode paint layer 306 is applied to asurface of a substrate (e.g., metal surface). The anode paint layer 306can function as an electrical anode for both the solar battery 302 andthe solar cell 304.

An ion bridge paint layer 308 is applied to the anode paint layer 306.In some implementations, the ion bridge paint layer 308 is applied toless than all of the anode paint layer 306, such that part of atop-surface of the anode paint layer 306 is exposed after the ion bridgepaint layer 308 is applied. In some implementations, the ion bridgepaint layer 308 can entirely cover one side of the anode paint layer306.

A photosensitized/battery cathode paint layer 310 is applied to the ionbridge paint layer 308. The photosensitized/battery cathode paint layer310 can have multiple functions, including serving as a photosensitizedlayer for absorbing photons and generating electron-hole pairs for thesolar cell 304, as well as serving as a battery cathode layer for thesolar battery 302.

A solar cell cathode paint layer 312 is applied to thephotosensitized/battery cathode paint layer 310. The solar cell cathodepaint layer 312 forms a cathode for the solar cell 304. In someimplementations, the solar cell cathode paint layer 312 is applied toless than the entire photosensitized/battery cathode paint layer 310,such that a part of a top-surface of the photosensitized % batterycathode paint layer 310 is exposed. The solar cell cathode paint layer312 can be semi-transparent or transparent to allow light to reach thephotosensitized % battery cathode paint layer 310.

A transparent protective layer 314 is applied to the solar cell cathodepaint layer 312. In some implementations, the transparent protectivelayer 314 encapsulates a portion or all of the exposed surfaces of theoutput-regulated solar cell 300, and can be electrically insulating. Thetransparent protective paint layer 314 forms a protective layer overpart or all of the condensed solar circuit 300 to protect the paintlayers from environmental effects (e.g., UV radiation, weather,water/humidity). In some implementations, the transparent protectivepaint layer 314 is semi-transparent, and/or only transparent to certainwavelengths ranges (e.g., transparent to visible wavelengths). In someimplementations, the transparent protective layer 314 is omitted,depending in part on application and/or environmental factors (e.g.,level of exposure to weather). When the transparent protective layer 314is omitted, the solar cell cathode paint layer 312 can function as aconductive protect layer (e.g., indium tin oxide).

In some implementations, multiple solar circuits are electricallyconnected together to form larger systems of circuits. The multiplesolar circuits can be of a same or of different types, and can beconnected together in series and/or in parallel, depending onfunctionality of the larger system. For example, multiple solar cellscan be connected in series to one or more solar batteries such thatmultiple solar cells can be used to charge a solar battery, increasingthroughput.

In some implementations, electrical contacts can be included in any ofthe solar circuits (e.g., solar circuits 100, 150, 200, 300) discussedherein. The electrical contacts can include a first contact (e.g.,metallic foil, metallic mesh, cold weld bonding compound, solder ball,alligator clip, or the like) affixed to an anode paint layer (e.g.,battery anode paint layer 206, anode paint layer 306, battery anodepaint layer 106). A second contact (e.g., metallic foil, metallic mesh,cold weld bonding compound, solder ball, alligator clip, or the like)can be affixed to a cathode paint layer (e.g., battery cathode paintlayer 110, solar cell cathode paint layer 210, photosensitized/batterycathode paint layer 310). The electrical contacts can be used to connectto the solar circuit to an external device (e.g., a mobile phone,computer, or other battery-operated device). The electrical contacts canalso be used to connect the solar circuit to other solar circuits, forexample, to daisy-chain a set of solar cell painted circuits, toincrease throughput for powering and/or charging a user device (e.g., acell phone or computer), or charging a solar battery.

Example Process for Producing Solar Paint Formulations

Solar circuits and devices, including those described herein withreference to FIGS. 1-3, include multiple layers of solar paint. Solarpaint can include various formulations selected to give the solar paintlayers applied with the particular solar paint different electrical(e.g., resistive/conductive), reactive (e.g., photo-reactive),dielectric (e.g., voltage breakdown) and physical properties (e.g.,viscosity). In some implementations, paint formulations are aqueous andinclude water, a solvent (e.g., ethanol), and/or an emulsifier.

Implementations of solar paints include resistor/conductor paint (e.g.,for resistor paint layers and conductor paint layers) and transistorpaint (e.g., for transistor paint layers). The resistor paint can be anaqueous composition including an acrylic material mixed with one or moreconductive materials. Examples of suitable acrylic materials includepolyacrylic acid (PAA), polymethyl acrylate (PMA), and polymethylmethacrylate (PMMA). Examples of suitable conductive materials includealuminum, graphite, activated carbon, amorphous carbon, tungsten, zinc,carbon black, conductive nanomaterial such as nanoparticles (e.g.,copper(II) oxide), and conductive polymers (e.g., polvaniline,spiro-OMeTAD, polyphenylene, poly(flurorene), polypyrene, polyazulene,polynapthalene, poly(pyrrole), polycarbazole, polyindole, polvazepine,poly(theiophene), poly(3,4-ethylenedioxythiophene), poly(p-phenylenesulfide), poly(acetylene), poly(p-phenylene vinylene)).

In some implementations, conductive nanomaterials (e.g., nanoparticles)are selected based in part on a transparency of the resultingresistor/conductor paint including the conductive nanomaterials.Additionally, deflocculants (e.g., sodium lauryl dodecasulfide or abasic salt like sodium carbonate or potassium carbonate) can be added tothe resist/conductor paint including the conducting nanomaterials toprevent flocculation, minimize surface energy of the dispersednanoparticles, and assist in dispersion of the nanomaterials and improvetransparency.

FIG. 4 is a flow chart of an example process for producing solar paint.Referring to FIG. 4, resistor/conductor paint can be prepared by process400. In 402, a suitable conductive material is combined with water toyield a mixture. In 404, a suitable acrylic material is combined withthe mixture and agitated gently, avoiding introduction of air bubbles,to yield the resistor/conductor paint. A weight ratio of the conductivematerial in the acrylic material determines, in part, a resistance ofthe resistor paint layer. For weight ratios of conductive material abovea conductivity threshold, the weight ratio of the conductive material inthe acrylic material determines, in part, the conductivity of theconductor paint layer.

The transistor paint can be a composition including a dielectricmaterial, where the dielectric material has a breakdown voltage thatcorresponds to a desired switching voltage of the transistor paintlayer, and a paint binder. The breakdown voltage is a minimum voltagethat causes a portion of an insulating material to become electricallyconductive. Examples of suitable dielectric materials for transistorpaint layers include low-k dielectric materials such as silicon dioxide,or silicon dioxide doped with carbon and/or fluorine. Acrylic orpolyurethane can be used as a paint binder material for the transistorpaint.

Conductor paints prepared according to the process of FIG. 4 can includen-type semiconductive materials as the conductive material, e.g., foruse as an electron conducting diode paint layer. Examples of n-typesemiconductive materials include carbon-based materials, such asgraphite powder, activated charcoal, and n-type carbon nanomaterialssuch as nanoparticles or nanotubes. The n-type semiconductive materialscan be doped with an n-type dopant, such as nitrogen, to reduce the workfunction of the semiconductive material, thus decreasing the forwardvoltage drop of the diode. For instance, graphite powder having adiameter of 50-800 μm can be used. The mass ratio of graphite can affectthe conductivity of the paint layer prepared using the conductor paint.In a specific example, the ratio of graphite powder to acrylic materialto water can be 4:1:1.

Conductor paints prepared according to the process of FIG. 4 can includep-type semiconductive materials as the conductive material, e.g., foruse as a hole conducting diode paint layer. Examples of p-typesemiconductive materials include p-type polymers (e.g.,poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)),hole-conducting nanomaterials (e.g., copper(I) oxide nanoparticles,copper(I) oxide nanoparticles, and nickel(I) oxide nanoparticles). Insome examples, a dispersant material, such as benzenesulfonic acid, canbe added to the water phase of the conductor paint to facilitatedispersion of the p-type semiconductive material in the water.

Implementations of solar paints can also include ion bridge paint (e.g.,for an ion bridge paint layer in a solar battery). Examples of suitableion bridge material include potassium ions mixed in an ion-conductingmaterial. Examples of suitable ion-conducting materials include polymerelectrolytes such as polyethylene oxide (PEO), polyacrylonitrile (PAN),polymethyl methacrylate (PMMA), and polyvinylidene fluoride (PVdF).

FIG. 5 is a flow chart of another example process for producing solarpaint. Referring to FIG. 5, ion bridge paint can be prepared by process500. In 502, a suitable ionic material is combined with water to yield amixture. In 504, a suitable ion-conducting material is combined with themixture and agitated gently, avoiding introduction of air bubbles, toyield the ion bridge paint.

Implementations of solar paints can also include electroluminescent orelectro-phosphorescent paint (e.g., for phosphorescent paint layers).Examples of suitable electroluminescent material includepoly(p-phenylene vinylene), polyflurorene, zinc sulfide doped withcopper, gallium arsenide, gallium nitride, rubidium polypyridine, andaluminum gallium indium phosphide. Examples of suitableelectro-phosphorescent materials include a polymer host such aspoly(N-vinylcarbazole) with an organometallic complex dopant such asIr(mppy)3, platinum, and other heavy metal complexes.

FIG. 6 is a flow chart of another example process for producing solarpaint. Referring to FIG. 6, electroluminescent/electro-phosphorescentpaint can be prepared by process 600. In 602, a suitableelectroluminescent or electro-phosphorescent material is combined withwater to yield a mixture. In an optional step 604, a suitable polymerhost is combined with the mixture and agitated gently, avoidingintroduction of air bubbles, to yield theelectroluminescent/electro-phosphorescent paint.

Implementations of solar paints can also include electron (anion)transport paint (e.g., for anode paint layers), photosensitizing paint(e.g., for photosensitized paint layers), and hole (cation) transportpaint (e.g., for cathode paint layers). These solar paints include oneor more of a fast ion conductor, an electron acceptor, a salt, and adye.

The fast ion conductor can be an anionic fast ion conductor (e.g., forelectron transport paint or photosensitizing paint) or a cationic fastion conductor (e.g., for hole transport paint). Examples of suitablefast ion conductors include anionic and cationic polyacrylamides,yttria-stabilized zirconia, beta-alumina, lanthanum trifluoride,beta-lead fluoride, silver iodide, copper(I) iodide, rubidium silveriodide, silver mercury iodide, silver sulfide, lead(II) chloride,strontium titanate, strontium stannate, hydrogen uranyl phosphatetetrahydrate, cerium(IV) oxide, zirconium hydrogen phosphate, lithiumperchlorate in polyethylene oxide, polyelectrolytes, and ionomers.

An electron acceptor for a particular paint layer can be selected, inpart, based on an injection efficiency of the electron acceptor relativeto a photosensitizer used in the particular paint layer. Examples ofsuitable electron acceptors include titanium dioxide (e.g., rutile oranatase titanium dioxide nanoparticles), zinc oxide, benzothiadiazole,benzotriazole, quinoxaline, phthalimide, diketopyrrolopyrrole,thienopyrazine, thiazole, triazine, cyanovinyl, cyano- andfluoro-substituted phenyl, iodine, rhodanine, naphthalamide, and acrylicacids.

Various different dyes can be used to create electronic solar paint.Selection of the dyes used to create electronic solar paint can dependin part on an optimal absorption spectrum for a particular application(e.g., tropical vs. arctic latitude, indoor vs. outdoor use).Additionally, an electronic solar paint can include one or moredifferent dyes for multiple-peak absorption spectra functionality. Insome implementations, the dye has high absorption (e.g., in the 500 nmrange, which corresponds to a dark bluish-green color), and has at leastone chromophore (functional group which is the source of thecolor/photoactive response) which undergoes excitation from a p to a p*highest-occupied molecular orbital (HOMO) on illumination. Examples ofsuitable dyes include copper phthalocyanine, zinc phthalocyanine,merocyanine, ruthenium-polypyridine, iron hexacyanoferrate,Ru-polypyridyl-complex sensitizers (e.g., cis-dithiocyanatobis(4,4′-dicarboxy-2,2′-bipyridine)ruthenium(I)).

In an electrolytic cell (meaning an aqueous cell or a cell in which asolid-state electrolyte mediates charge transfer) an electron acceptorcan be any oxidizing agent whose reduced state can itself be oxidized bythe photosensitizer (i.e. the dye or pigment) in an energeticallyfavorable way, and does not cause or accelerate irreversible chemicaldegradation of the cell. Salts of lithium, potassium, and iodine can beused. In some implementations, the charge can be mediated entirely bythe salt (e.g. reduction from ΔI2 to 2I- and oxidation from 2I- to ΔI2),and can be galvanically favorable in the absence of water. Examples ofsuitable salts include potassium iodide.

The electron transport paint is an aqueous composition that includes ananionic fast ion conductor and a salt in a weight ratio ofwater:salt:anionic fast ion conductor. In some implementations theelectron transport paint includes an anionic fast ion conductor and asalt in a weight ratio of water:salt:anionic fast ion conductor of60:10:1. In some implementations, the electron transport paint is anaqueous composition that includes an anionic fast ion conductor, anelectron acceptor, and a salt in a weight ratio of water:electronacceptor:salt:anionic fast ion conductor of 60:10:10:1. A specific massratio of salt and/or an electron acceptor in the electron transportpaint is based, in part, on a molar mass of the specific salt and/orelectron acceptor used in the composition.

In some implementations, the electron transport paint is an aqueouscomposition that includes an anionic fast ion conductor and a conductivematerial (e.g., graphite), for example, for a battery anode paint layer.

FIG. 7 is a flow chart of another example process for producing solarpaint. Referring to FIG. 7, an electron transport paint can be preparedby process 400. In 702, a suitable salt is dissolved in water to yield asalt solution. In 704, which is optional, a suitable electron acceptoris combined with the salt solution to yield a mixture. The mixture canbe agitated (e.g., stirred) to remove clumps. The mixture is allowed tosit, such that the electron acceptor settles to the bottom of thecontainer. After all of the air bubbles have dissipated from themixture, the anionic fast ion conductor is combined with the mixture in706 and dissolved to yield electron transport paint. The electrontransport paint is in the form of a suspension, with the electronacceptor particles suspended in the paint. In one example, an electrontransport paint is an aqueous suspension that includes titanium dioxide,potassium iodide, and anionic polyacrylamide in a weight ratio ofwater:titanium dioxide:potassium iodide:anionic polyacrylamide of60:10:10:1. For a small cell (e.g., less than 100 cm²), 1 mL of water issufficient to cover 8 cm² of the cell.

The photosensitizing paint is an aqueous composition that includes ananionic fast ion conductor and a dye in a weight ratio of water:anionicfast ion conductor:dye of 6:1:1.

FIG. 8 is a flow chart of another example process for producing solarpaint. Referring to FIG. 8, photosensitizing paint can be prepared byprocess 800. In 802, a suitable dye is combined with water to yield amixture. In 804, a suitable anionic fast ion conductor is combined withthe mixture and agitated gently, avoiding introduction of air bubbles,to yield the photosensitizing paint. The consistency and color of thephotosensitizing paint changes as the anionic fast ion conductordissolves. The photosensitizing paint is in the form of a suspension,with dye suspended in the paint. In one example, a photosensitizingpaint is an opaque dark greenish-blue aqueous suspension that includesanionic polyacrylamide and copper phthalocyanine in a weight ratio ofwater:anionic polyacrylamide:copper phthalocyanine of 6:1:1.

The hole transport paint is an aqueous composition that includes acationic fast ion conductor in a weight ratio of water:cationic fast ionconductor of 60:1. FIG. 9 is a flow chart of another example process forproducing solar paint. Referring to FIG. 9, hole transport paint can beprepared by process 900. In 902, a suitable cationic fast ion conductoris dissolved in water to yield the hole transport paint. In one example,a hole transport paint is an aqueous composition that includes cationicpolyacrylamide in a weight ratio of water:cationic polyacrylamide 60:1.

In some implementations, a hole transport paint formulation can includea cationic fast ion conductor and a dye (e.g., Prussian blue), forexample, for a battery cathode paint layer.

In some implementations, a solar paint can be formulate such that apaint layer applied with the solar paint has multiple functionality. Forexample, a photosensitized/battery cathode paint formulated to apply aphotosensitized/battery cathode paint layer, as discussed with referenceto FIG. 3, includes one or more of a cationic fast ion conductor and adye.

FIG. 10 is a flow chart of another example process for producing solarpaint. Referring to FIG. 10, photosensitizing/battery cathode paint canbe prepared by process 1000. In 1002, a suitable dye is combined withwater to yield a mixture. In 1004, a suitable cationic fast ionconductor is combined with the mixture and agitated gently, avoidingintroduction of air bubbles, to yield the photosensitizing/batterycathode paint. The consistency and color of the photosensitizing paintchanges as the cationic fast ion conductor dissolves. Thephotosensitizing paint is in the form of a suspension, with dyesuspended in the paint. In one example, a photosensitizing paint is anopaque dark greenish-blue aqueous suspension that includes cationicpolyacrylamide and copper phthalocyanine in a weight ratio ofwater:cationic polyacrylamide:copper phthalocyanine of 6:1:1.

Example Process for Producing Solar Paint Circuit

FIG. 11 is a flow chart of an example process for painting a solar paintcircuit. In general, a solar circuit (e.g., solar circuit 100, 150, 200,300) can be fabricated according to process 1100, as shown in the flowdiagram in FIG. 11. In 1102, a substrate is provided. Substrates caninclude metal, wood, plaster, fabric, or the like. A substrate canfurther include a wire mesh or foil affixed to a base structuralmaterial, to provide electrical conductivity. In 1104, one or more paintlayers are applied to a surface of the substrate, where each paint layerincludes a conductive paint formulation. In some implementations, eachapplied paint layer is allowed to dry prior to the application of asubsequent layer.

The conductive paint formulation has a resistance defined, in part, by aconcentration of conductive material included in the conductive paintformulation. For example, a lower concentration of the conductivematerial (e.g., carbon black) included in the conductive paintformulation provides a higher resistance than a conductive paintformulation having a higher concentration of the same conductivematerial.

In some implementations, multiple coatings of a same conductive paintformulation can be applied to form a layer of a desired thickness, wherethe desired thickness is greater than a thickness of a single appliedlayer.

FIG. 12 is a flow chart of another example process for painting a paintcircuit. Referring to FIG. 12, a paint circuit (e.g., solar cell 202, orsolar cell 104) can be fabricated according to process 1200. In 1202,electron transport paint is applied to a substrate and allowed to dry toyield a layer of the electron transport paint in direct contact with thesubstrate. Substrates can be electrically conducting or electricallynon-conducting. Suitable electrically insulating substrates includewood, plaster, and plastic. Electrically conducting substrates caninclude substrates having relatively low work-function, low financialcost, low susceptibility to oxidation, and high physical strengthrelative to the one or more paint layers. Suitable electricallyconducting substrates include aluminum mesh, aluminum foil, as well aszinc, magnesium, nickel, copper, silver, gold, and platinum. In someimplementations, one or more additional layers of the electron transportpaint can be subsequently applied. In 1204, photosensitizing paint isapplied to the to the electron transport paint layer and allowed to dryto yield a layer of the photosensitizing paint in direct contact withthe layer of the electron transport paint. In some implementations, oneor more additional layers of the photosensitizing paint can besubsequently applied. In 1206, hole transport paint is applied to thephotosensitizing paint layer and allowed to dry to yield a layer of thehole transport paint in direct contact with the layer of thephotosensitizing paint layer. The hole transport layer is typicallytransparent. In some implementations, the electron transport layer istransparent in addition to or in place of the hole transport layer beingtransparent.

FIG. 13 is a flow chart 1300 of another example process for painting apaint circuit, for example, solar paint circuit 100 depicted in FIG. 1A.A battery anode paint is applied to the substrate to yield a layer ofthe battery anode paint in direct contact (e.g., physical and/orelectrical) with the substrate (1302). Anion bridge paint is applied toless than all of the battery anode paint layer to yield a layer of ionbridge paint in direct contact with the battery anode paint layer(1304). A battery cathode paint is then applied to the ion bridge paintlayer to yield a layer of battery cathode paint in direct contact withthe ion bridge paint layer (1306). A solar cell anode paint is appliedto less than all of the battery cathode paint layer to yield a layer ofsolar cell anode paint in direct contact with the battery cathode paintlayer (1308). A photosensitized paint is applied to the solar cell anodepaint layer to yield a layer of photosensitized paint in direct contactwith the solar cell anode paint layer (1310). A solar cell cathode paintis applied to the photosensitized paint layer to yield a layer of solarcell cathode paint in direct contact with the photosensitized paintlayer (1312). A diode paint circuit is formed between the battery anodepaint layer and the solar cell cathode layer (1314). The diode paintcircuit is formed by applying an electron conducting paint to less thanall of the battery anode paint layer to yield a layer of electronconducting paint in direct contact with the battery anode paint layer. Ahole conducting paint layer is applied to the electron conducting paintlayer to yield a layer of hole conducting paint in direct contact withthe electron conducting paint layer. The diode paint circuit is formedand physically separated from the photosensitized paint layer, the solarcell anode paint layer, the battery cathode paint layer, and the ionbridge paint layer. A transparent protective paint is applied to thesolar cell cathode paint layer to yield a layer of transparentprotective paint in direct contact with the solar cell cathode paintlayer (1316).

FIG. 14 is a flow chart 1400 of another example process for painting apaint circuit, for example, solar paint circuit 150 depicted in FIG. 1B.A transistor paint is applied to less than all of the battery cathodelayer to yield a layer of transistor paint in direct contact with thebattery cathode layer and in electrical contact with the solar cellanode paint layer (1402). A light-emitting circuit is formed between thetransistor paint layer and the transparent protective paint layer(1404). Forming the light-emitting circuit includes applying an electronconducting paint (e.g., an anode paint) to less than all of thetransistor paint layer to yield a layer of electron conducting paint indirect contact with the transistor paint layer. A phosphorescent paintis applied to the electron conducting paint layer to yield a layer ofphosphorescent paint in direct contact with the electron conductingpaint layer. A hole conducting paint (e.g., a cathode paint) is appliedto the phosphorescent paint layer to yield a layer of hole conductingpaint in direct contact with the phosphorescent paint layer. Thelight-emitting circuit is formed and is physically separated from thephotosensitized paint layer. A conductor paint is applied to less thanall of the battery anode paint layer to yield a layer of conductor paintin direct contact with the battery anode paint layer and thelight-emitting circuit and is physically separated from each of the ionbridge paint layer, the battery cathode paint layer, and the transistorpaint layer (1406).

FIG. 15 is a flow chart 1500 of another example process for painting apaint circuit, for example, solar paint circuit 200 depicted in FIG. 2.An anode paint is applied to the substrate to yield a layer of anodepaint in direct contact with the substrate (1502). An ion bridge paintis applied to less than all of the anode paint layer to yield a layer ofion bridge paint in direct contact with the anode paint layer (1504). Aphotosensitized/battery cathode paint is applied to the ion bridge paintlayer to yield a layer of photosensitized/battery cathode paint indirect contact with the ion bridge paint layer (1506). A solar cellcathode paint to less than all of the photosensitized/battery cathodepaint layer to yield a layer of solar cell cathode paint in directcontact with the photosensitized/battery cathode paint layer (1508). Atransparent protective layer paint is applied to the solar cell cathodepaint layer to yield a layer of transparent protective paint in directcontact with the solar cell cathode paint layer (1510).

FIG. 16 is a flow chart 1600 of another example process for painting apaint circuit, for example, solar paint circuit 300 depicted in FIG. 3.An anode paint is applied to the substrate to yield a layer of anodepaint in direct contact with the substrate (1602). A photosensitizedpaint is applied to less than all of the solar cell anode paint layer toyield a layer of photosensitized paint in direct contact with the solarcell anode paint layer (1604). An output regulator circuit is formed ontop of the solar cell anode paint layer (1606). The output regulatorcircuit is formed by a process including applying a resistor paint toless than all of the solar cell anode paint layer to yield a layer ofresistor paint in direct contact with the solar cell anode paint layerand adjacent and in electrical contact to the photosensitized paintlayer. A transistor paint is applied to the resistor paint layer toyield a layer or transistor paint in direct contact with the resistorpaint layer. A solar cell cathode paint is applied to thephotosensitized paint layer and the transistor paint layer to yield alayer of solar cell cathode paint in direct contact with thephotosensitized paint layer and the transistor paint layer (1608). Atransparent protective paint is applied to the solar cell cathode paintlayer to yield a layer of transparent protective paint in direct contactwith the solar cell cathode paint layer (1610).

In some implementations, a capacitor circuit element can be formed bypainting a dielectric paint layer between two conductive paint layers(e.g., a cathode paint layer and an anode paint layer), such that aspecific capacitance and breakdown voltage of the capacitor depends, inpart, on the dielectric breakdown of the dielectric paint layer and thedielectric paint layer thickness.

In some implementations, perovskite-based solar paint can be used.Perovskites are lead-based, and therefore could be used to create ahigh-performing solar paint for circumstances in which the use of alead-based paint may be appropriate.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyfeatures or of what can be claimed, but rather as descriptions offeatures specific to particular embodiments of the described paintedcircuits and painted circuit elements. Though the painted circuits andpainted circuit elements examples are described herein as havingparticular layer structures, they should not be read as limiting. Forexample, the painted circuits and painted circuit elements are describedas operating in a “top-down” fashion where the devices are paintedlayer-by-layer such that the top layer is the top of the device. Whileprocesses are depicted in the drawings in a particular order, thisshould not be understood as requiring that such processes be performedin the particular order shown or in sequential order, or that allillustrated processes be performed, to achieve desirable results. Forexample, the painted circuits and painted circuit elements may also bepainted in a “bottom-up” fashion where the function of the devices isupside relative to their fabrication order. Additionally, “flip-chip”configurations can be imagined where two substrates are individuallypainted with paint layers and then combined.

Other complex painted circuit elements can be created using thetechniques and compositions described herein. For example, paintedantenna elements. Additionally, active matrices of multiple smallersub-elements (e.g., embedded painted circuit elements) can be createdusing the techniques and compositions described herein.

Thus, particular embodiments of the subject matter have been described.Other embodiments are within the scope of the following claims. In somecases, the actions recited in the claims can be performed in a differentorder and still achieve desirable results. In addition, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In certain implementations, multitasking and parallelprocessing may be advantageous.

What is claimed is:
 1. A painted circuit, comprising: a substrate; andone or more paint layers applied to the substrate, the one or more paintlayers each forming an electrical component of the painted circuit,wherein: a given paint layer of the one or more paint layers comprises aconductive paint formulation having a resistance that is defined by aconcentration of conductive material that is included in the conductivepaint formulation and a thickness of the given paint layer; and lowerconcentrations of the conductive material included in the conductivepaint formulation provide a higher resistance than higher concentrationsof conductive material; and wherein the one or more paint layers ofconductive paint comprise: a battery anode paint layer applied to thesubstrate; an ion bridge paint layer applied to less than all of thebattery anode paint layer; and a battery cathode paint layer applied tothe ion bridge paint layer; a solar cell anode paint layer applied toless than all of the battery cathode paint layer; a photosensitizedpaint layer applied to the solar cell anode paint layer; and a solarcell cathode paint layer applied to the photosensitized paint layer. 2.The painted circuit of claim 1, wherein the one or more paint layers ofconductive paint further comprise: a diode paint circuit that is formedbetween the battery anode paint layer and the solar cell cathode paintlayer.
 3. The painted circuit of claim 2, wherein the diode paintcircuit is physically separated from each of the photosensitized paintlayer, the solar cell anode paint layer, the battery cathode paintlayer, and the ion bridge paint layer.
 4. The painted circuit of claim3, wherein the diode paint circuit includes an electron conducting paintlayer and a hole conducting paint layer.
 5. The painted circuit of claim1, further comprising a transparent protective layer applied to thesolar cell cathode paint layer.
 6. The painted circuit of claim 4, inwhich the electron conducting paint layer comprises a n-typesemiconductor.
 7. The painted circuit of claim 4, in which the holeconducting paint layer comprises a p-type semiconductor.
 8. The paintedcircuit of claim 7, in which the p-type semiconductor comprises p-typenanoparticles.
 9. The painted circuit of claim 5, further comprising: atransistor paint layer applied to less than all of the battery cathodepaint layer and in electrical contact with the solar cell anode paintlayer; a light-emitting circuit that is formed between the transistorpaint layer and the transparent protective layer.
 10. The paintedcircuit of claim 9, wherein the light-emitting circuit is physicallyseparated from the photosensitized paint layer.
 11. The painted circuitof claim 9, wherein the light-emitting circuit includes an electronconducting paint layer, a hole conducting paint layer, and aphosphorescent paint layer between the electron conducting paint layerand the hole conducting paint layer.
 12. The painted circuit of claim 9,further comprising a conductor paint layer that is formed between thebattery anode paint layer and the light-emitting circuit, wherein theconductor paint layer is physically separated from each of the ionbridge paint layer, the battery cathode paint layer, and the transistorpaint layer.
 13. The painted circuit of claim 9, wherein the transistorpaint layer comprises a composition including a dielectric material thathas a breakdown voltage that corresponds to a switching voltage of thetransistor paint layer.
 14. A painted circuit, comprising: a substrate;and one or more paint layers applied to the substrate, the one or morepaint layers each forming an electrical component of the paintedcircuit, wherein: a given paint layer of the one or more paint layerscomprises a conductive paint formulation having a resistance that isdefined by a concentration of conductive material that is included inthe conductive paint formulation and a thickness of the given paintlayer; and lower concentrations of the conductive material included inthe conductive paint formulation provide a higher resistance than higherconcentrations of conductive material; and wherein the one or more paintlayers of conductive paint comprise: an anode paint layer applied to thesubstrate; a further ion bridge paint layer applied to less than all ofthe anode paint layer; a photosensitized/battery cathode paint layerapplied to the further ion bridge paint layer; a further solar cellcathode paint layer applied to less than all of thephotosensitized/battery cathode paint layer; and a transparentprotective layer applied to the further solar cell cathode paint layer.15. The painted circuit of claim 14, wherein the anode paint layercomprises an aqueous composition including: an anionic fast ionconductor; and a salt in a weight ratio of water, wherein the salt inthe weight ratio of water:salt:anionic fast ion conductor is 60:10:1.16. The painted circuit of claim 14, wherein the further ion bridgepaint layer comprises an aqueous composition including an ionic materialand an ion-conducting polymer in a weight ratio of water.
 17. Thepainted circuit of claim 14, further comprising two or more contacts,each contact comprising a metallic foil affixed to an anode paint layeror a photosensitized/battery cathode paint layer and in electricalcontact with the anode paint layer or the photosensitized/batterycathode paint layer, respectively.
 18. A painted circuit, comprising: asubstrate; and one or more paint layers applied to the substrate, theone or more paint layers each forming an electrical component of thepainted circuit, wherein: a given paint layer of the one or more paintlayers comprises a conductive paint formulation having a resistance thatis defined by a concentration of conductive material that is included inthe conductive paint formulation and a thickness of the given paintlayer; and lower concentrations of the conductive material included inthe conductive paint formulation provide a higher resistance than higherconcentrations of conductive material; and wherein the one or more paintlayers of conductive paint comprise: a further solar cell anode paintlayer applied to the substrate; a further photosensitized paint layerapplied to less than all of the further solar cell anode paint layer; anoutput regulator circuit that is formed on top of the further solar cellanode paint layer, the output regulator circuit comprising a resistorpaint layer and transistor paint layer, wherein: the resistor paintlayer is applied to the further solar cell anode paint layer and isapplied adjacent to the further photosensitized layer; and thetransistor paint layer is applied to the resistor paint layer; a yetfurther solar cell cathode paint layer applied to the furtherphotosensitized paint layer and the transistor paint layer; and atransparent protective paint layer applied to the yet further solar cellcathode paint layer.
 19. The painted circuit of claim 18, wherein thetransistor paint layer comprises a composition including a dielectricmaterial that has a breakdown voltage that corresponds to a switchingvoltage of the transistor paint layer.
 20. The painted circuit of claim18, further comprising two or more contacts, each contact comprising ametallic foil affixed to a solar further cell anode paint layer or a yetfurther solar cell cathode paint layer and in electrical contact withthe further solar cell anode paint layer or the yet further solar cellcathode paint layer, respectively.